Procedures

In this section containing specifications of procedures, the following notation is used to specify parameters and return values:

(f arg_1 arg_2 ···) -> something

Indicates a function f takes the parameters arg_1 arg_2 ··· and returns a value of the type something. If something is unspecified, then what f returns is implementation-dependant; this SRFI does not specify what it returns, and in order to write portable code, the return value should be ignored.

vec

The argument in this place must be a vector, i.e. it must satisfy the predicate vector?.

i, j, start, size

The argument in this place must be a nonnegative integer, i.e. it must satisfy the predicates integer? and either zero? or positive?. The third case of it indicates the index at which traversal begins; the fourth case of it indicates the size of a vector.

end

The argument in this place must be a positive integer, i.e. it must satisfy the predicates integer? and positive?. This indicates the index directly before which traversal will stop — processing will occur until the the index of the vector is end. It is the closed right side of a range.

f

The argument in this place must be a function of one or more arguments, returning exactly one value.

pred?

The argument in this place must be a function of one or more arguments that returns one value, which is treated as a boolean.

x, y, z, seed, knil, fill, key, value

The argument in this place may be any Scheme value.

[something]

Indicates that something is an optional argument; it needn't necessarily be applied. Something needn't necessarily be one thing; for example, this usage of it is perfectly valid: [start [end]] and is indeed used quite often.

something ···

Indicates that zero or more somethings are allowed to be arguments.

something_1 something_2 ···

Indicates that at least one something must be arguments.

something_1 something_2 ··· something_n

Exactly equivalent to the previous argument notation, but this also indicates that n will be used later in the procedure description.

It should be noted that all of the procedures that iterate across multiple vectors in parallel stop iterating and produce the final result when the end of the shortest vector is reached. The sole exception is vector=, which automatically returns #f if the vectors' lengths vary.

Constructors

[procedure](vector-unfold f length initial-seed ···) -> vector

The fundamental vector constructor. Creates a vector whose length is length and iterates across each index k between 0 and length, applying f at each iteration to the current index and current seeds, in that order, to receive n + 1 values: first, the element to put in the kth slot of the new vector and n new seeds for the next iteration. It is an error for the number of seeds to vary between iterations.

Allocates a new vector whose length is end - start and fills it with elements from vec, taking elements from vec starting at index start and stopping at index end. start defaults to 0 and end defaults to the value of (vector-length vec). If end extends beyond the length of vec, the slots in the new vector that obviously cannot be filled by elements from vec are filled with fill, whose default value is unspecified.

Examples:

(vector-copy '#(a b c d e f g h i))
;=> #(a b c d e f g h i)

(vector-copy '#(a b c d e f g h i) 6)
;=> #(g h i)

(vector-copy '#(a b c d e f g h i) 3 6)
;=> #(d e f)

(vector-copy '#(a b c d e f g h i) 6 12 'x)
;=> #(g h i x x x)

[procedure](vector-reverse-copy vec [start [end]]) -> vector

Like vector-copy, but it copies the elements in the reverse order from vec.

Example:

(vector-reverse-copy '#(5 4 3 2 1 0) 1 5)
;=> #(1 2 3 4)

[procedure](vector-append vec ···) -> vector

Returns a newly allocated vector that contains all elements in order from the subsequent locations in vec ···.

Examples:

(vector-append '#(x) '#(y))
;=> #(x y)

(vector-append '#(a) '#(b c d))
;=> #(a b c d)

(vector-append '#(a #(b)) '#(#(c)))
;=> #(a #(b) #(c))

[procedure](vector-concatenate list-of-vectors) -> vector

Appends each vector in list-of-vectors. This is equivalent to:

(apply vector-append list-of-vectors)

However, it may be implemented better.

Example:

(vector-concatenate '(#(a b) #(c d)))
;=> #(a b c d)

Predicates

[procedure](vector-empty? vec) -> boolean

Returns #t if vec is empty, i.e. its length is 0, and #f if not.

Examples:

(vector-empty? '#(a))
;=> #f

(vector-empty? '#(()))
;=> #f

(vector-empty? '#(#()))
;=> #f

(vector-empty? '#())
;=> #t

[procedure](vector= elt=? vec ···) -> boolean

Vector structure comparator, generalized across user-specified element comparators. Vectors a and b are considered equal by vector= iff their lengths are the same, and for each respective elements E_a and E_b, (elt=? E_a E_b) returns a true value. Elt=? is always applied to two arguments. Element comparison must be consistent with eq; that is, if (eq? E_a E_b) results in a true value, then (elt=? E_a E_b) must also result in a true value. This may be exploited to avoid unnecessary element comparisons. (The reference implementation does, but it does not consider the situation where elt=? is in fact itself eq? to avoid yet more unnecessary comparisons.)

If there are only zero or one vector arguments, #t is automatically returned. The dynamic order in which comparisons of elements and of vectors are performed is left completely unspecified; do not rely on a particular order.

Examples:

(vector= eq? '#(a b c d) '#(a b c d))
;=> #t

(vector= eq? '#(a b c d) '#(a b d c))
;=> #f

(vector= = '#(1 2 3 4 5) '#(1 2 3 4))
;=> #f

(vector= = '#(1 2 3 4) '#(1 2 3 4))
;=> #t

The two trivial cases.

(vector= eq?)
;=> #t

(vector= eq? '#(a))
;=> #t

Note the fact that we don't use vector literals in the next two — it is unspecified whether or not literal vectors with the same external representation are eq?.

(vector= eq? (vector (vector 'a)) (vector (vector 'a)))
;=> #f

(vector= equal? (vector (vector 'a)) (vector (vector 'a)))
;=> #t

Iteration

[procedure](vector-fold kons knil vec_1 vec_2 ···) -> value

The fundamental vector iterator. Kons is iterated over each index in all of the vectors, stopping at the end of the shortest; kons is applied as (kons i state (vector-ref vec_1 i) (vector-ref vec_2 i) ···) where state is the current state value — the current state value begins with knil, and becomes whatever kons returned at the respective iteration —, and i is the current index.

Constructs a new vector of the shortest size of the vector arguments. Each element at index i of the new vector is mapped from the old vectors by (f i (vector-ref vec_1 i) (vector-ref vec_2 i) ···). The dynamic order of application of f is unspecified.

Similar to vector-map, but rather than mapping the new elements into a new vector, the new mapped elements are destructively inserted into vec_1. Again, the dynamic order of application of f unspecified, so it is dangerous for f to apply either vector-ref or vector-set! to vec_1 in f.

[procedure](vector-for-each f vec_1 vec_2 ···) -> unspecified

Simple vector iterator: applies f to each index in the range [0, length), where length is the length of the smallest vector argument passed, and the respective list of parallel elements from vec_1 vec_2 ··· at that index. In contrast with vector-map, f is reliably applied to each subsequent elements, starting at index 0, in the vectors.

Counts the number of parallel elements in the vectors that satisfy pred?, which is applied, for each index i in the range [0, length) — where length is the length of the smallest vector argument —, to i and each parallel element in the vectors at that index, in order.

Finds & returns the index of the first elements in vec_1 vec_2 ··· that do not satisfy pred?. If all the values in the vectors satisfy pred? until the end of the shortest vector, this returns #f. This is equivalent to:

Similar to vector-index and vector-index-right, but instead of searching left to right or right to left, this performs a binary search. cmp should be a procedure of two arguments and return a negative integer, which indicates that its first argument is less than its second, zero, which indicates that they are equal, or a positive integer, which indicates that the first argument is greater than the second argument. An example cmp might be:

Finds the first set of elements in parallel from vec_1 vec_2 ··· for which pred? returns a true value. If such a parallel set of elements exists, vector-any returns the value that pred? returned for that set of elements. The iteration is strictly left-to-right.

[procedure](vector-every pred? vec_1 vec_2 ···) -> value or #f

If, for every index i between 0 and the length of the shortest vector argument, the set of elements (vector-ref vec_1 i) (vector-ref vec_2 i) ··· satisfies pred?, vector-every returns the value that pred? returned for the last set of elements, at the last index of the shortest vector. The iteration is strictly left-to-right.

Mutators

[procedure](vector-swap! vec i j) -> unspecified

Swaps or exchanges the values of the locations in vec at i & j.

[procedure](vector-fill! vec fill [start [end]]) -> unspecified

[R5RS+] Assigns the value of every location in vec between start, which defaults to 0 and end, which defaults to the length of vec, to fill.

[procedure](vector-reverse! vec [start [end]]) -> unspecified

Destructively reverses the contents of the sequence of locations in vec between start and end. Start defaults to 0 and end defaults to the length of vec. Note that this does not deeply reverse.

Copies a block of elements from source to target, both of which must be vectors, starting in target at tstart and starting in source at sstart, ending when send - sstart elements have been copied. It is an error for target to have a length less than tstart + (send - sstart). Sstart defaults to 0 and send defaults to the length of source.

Like vector-copy!, but this copies the elements in the reverse order. It is an error if target and source are identical vectors and the target & source ranges overlap; however, if tstart = sstart, vector-reverse-copy! behaves as (vector-reverse! target tstart send) would.

Conversion

[procedure](vector->list vec [start [end]]) -> proper-list

[R5RS+] Creates a list containing the elements in vec between start, which defaults to 0, and end, which defaults to the length of vec.

[procedure](reverse-vector->list vec [start [end]]) -> proper-list

Like vector->list, but the resulting list contains the elements in reverse between the the specified range.

[procedure](list->vector proper-list [start [end]])

[R5RS+] Produce a vector containing the elements in proper-list, which must be a proper list, between start, whose default is 0, and end, whose default is the length of list. It is suggested that if the length of list is known in advance, the start and end arguments be passed, so that list->vector need not call length itself.

[procedure](reverse-list->vector proper-list [start [end]]) -> vector

Like list->vector, but the resulting list contains the elements in reverse of proper-list.

Version history

License

The reference implementation is subject to the following copyright.

Copyright (C) Taylor Campbell (2003). All rights reserved.
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